Dynamoelectric machines such as turbine generators typically employ a retaining ring to contain a generator's rotor end windings. Such a ring, for example, may be constructed of a steel alloy and is generally attached to a generator's rotor body by an interference fit. The rotor end windings and the rotation forces developed during synchronous operating speeds tend to apply large amounts of stress to portions of the retaining ring. Because such stress forces are expected, retaining rings tend to be designed in such a way that any cracks which can eventually lead to ring failure are typically visible before ring failure occurs. In other words, there is a critical crack size such that cracks larger than that size are indicative of an impending failure of the retaining ring and that cracks can be smaller than this critical crack size, yet still be visibly detectable.
One method of inspecting a retaining ring for visible cracks involves shutting down the generator to a complete stop. The stopped unit may take upwards of 24 hours before it is cool enough to comfortably disassemble. Once disassembled, the unit can be inspected such as by using bore scopes to inspect difficult to reach portions of the generator. Once inspection is complete, then the unit can be reassembled which takes additional time before the generator can be restarted. In a worst case scenario, if a crack in the retaining ring exceeds the critical crack size before an outage and inspection of the generator can be completed, the retaining ring may fail causing severe damage to the rotating and stationary components of the generator.